linux-kernel - [PATCH 4.19 34/86] cifs: dont leak -EAGAIN for stat() during reconnect

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Message-Id: <20200310124532.618767487@linuxfoundation.org>
Date:   Tue, 10 Mar 2020 13:44:58 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ronnie Sahlberg <lsahlber@...hat.com>,
        Steve French <stfrench@...rosoft.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>,
        Aurelien Aptel <aaptel@...e.com>
Subject: [PATCH 4.19 34/86] cifs: dont leak -EAGAIN for stat() during reconnect

From: Ronnie Sahlberg <lsahlber@...hat.com>

commit fc513fac56e1b626ae48a74d7551d9c35c50129e upstream.

If from cifs_revalidate_dentry_attr() the SMB2/QUERY_INFO call fails with an
error, such as STATUS_SESSION_EXPIRED, causing the session to be reconnected
it is possible we will leak -EAGAIN back to the application even for
system calls such as stat() where this is not a valid error.

Fix this by re-trying the operation from within cifs_revalidate_dentry_attr()
if cifs_get_inode_info*() returns -EAGAIN.

This fixes stat() and possibly also other system calls that uses
cifs_revalidate_dentry*().

Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>
Reviewed-by: Aurelien Aptel <aaptel@...e.com>
CC: Stable <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/cifs/inode.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2003,6 +2003,7 @@ int cifs_revalidate_dentry_attr(struct d
 	struct inode *inode = d_inode(dentry);
 	struct super_block *sb = dentry->d_sb;
 	char *full_path = NULL;
+	int count = 0;
 
 	if (inode == NULL)
 		return -ENOENT;
@@ -2024,15 +2025,18 @@ int cifs_revalidate_dentry_attr(struct d
 		 full_path, inode, inode->i_count.counter,
 		 dentry, cifs_get_time(dentry), jiffies);
 
+again:
 	if (cifs_sb_master_tcon(CIFS_SB(sb))->unix_ext)
 		rc = cifs_get_inode_info_unix(&inode, full_path, sb, xid);
 	else
 		rc = cifs_get_inode_info(&inode, full_path, NULL, sb,
 					 xid, NULL);
-
+	if (rc == -EAGAIN && count++ < 10)
+		goto again;
 out:
 	kfree(full_path);
 	free_xid(xid);
+
 	return rc;
 }